A bubble chamber study of pion photo-production from hydrogen

Scarr, James M (1963) A bubble chamber study of pion photo-production from hydrogen. PhD thesis, University of Glasgow.

Abstract

A review of experimental and theoretical aspects of pion photoproduction from nucleons is given together with a discussion of the relation between the photoproduction of positive pions from protons and pion-nucleon scattering. The existing experimental data is shown to be insufficient to confirm the theoretical predictions for photoproduction from hydrogen near threshold which are necessary to resolve an apparent inconsistency in the low energy data on pion-nucleon scattering and photoproduction. A bubble chamber specially adapted for use with a high energy photon beam has been developed. The containment of any desired target material in a tube passing through the chamber and the ability to operate with either propane or freon ( CF3 BR ) gives a versatile method for the study of reactions induced by high energy photons. The apparatus and the choice of operating conditions are described. The method of measurement of events and their analysis from stereo-photographs is also described and the accuracy of the analysis discussed. The chamber, operating as a propane chamber, has been used to study positive pion production from hydrogen for photon energies 165 - 211 Mev. Protons from neutral pion production were also recorded. The determination of the scanning efficiency for finding events and its dependunce on track length is discussed and the scanning efficiency for accepted events is shown to be high. Angular distributions for TT+-photoproduction are given and the energy dependence of the cross sections determined. The present results lead to an essentially constant value for the usual parameter a+0 = 13,3 +/- 0,8, 10-30 cm2/ster. in the energy range Er = 169 - 206 Mev in contrast to the marked decrease of at with increasing photon energy predicted by dispersion theory. The results are compared with the data of other workers. A discrepancy between theory and experimental results appears well established above 170 Mev. Possible reasons for this discrepancy are discussed and reasons are given why the theory might be expected to be more reliable closer to the photoproduction threshold.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: P I Dee
• Keywords: Atomic physics
• Date of Award: 1963
• Depositing User: Enlighten Team
• Unique ID: glathesis:1963-73612
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jun 2019 08:56
• Last Modified: 14 Jun 2019 08:56
• URI: https://theses.gla.ac.uk/id/eprint/73612